Nowadays, motor vehicles are equipped with external and/or roof antennas virtually as standard. Such antennas generally serve to receive radio programs.
However, many of the motor vehicle antennas currently in use also comprise antenna means and radiating elements, for example for a geostationary locating system, i.e. a positioning system (GPS system), and additional antenna means for mobile communications.
As different frequencies, for example what is known as the 900 MHz band, the 1,800 MHz band, the 1,900 MHz band or else for example the UMTS frequencies (i.e. in the 1,920 to 2,170 MHz range), are important in mobile communications, motor vehicle antennas currently in use are frequently configured as what are known as multiband antennas which can be used in all these frequency ranges.
Known in principle are disk-type antennas which can be integrated, for example, in a rear pane of a motor vehicle window. Such disk-type antennas generally have in this case in the window a printed circuit which acts as an antenna and which can be used for example also as a heating field.
Also known are antennas which can be bonded to a rear window. The radiator is located on the outside of the window. The underside of the antenna base (antenna housing) is for this purpose bonded to the outer surface of the window, the counterpiece, which interacts with the antenna, being bonded on the inside of the window immediately below the antenna base, generally with the same or a smaller size, so that signals can be transmitted between the antenna base, which is located on the outside, and the electrical opposing surface, which is located on the inside of the window.
Otherwise, antennas are generally often arranged on the bodywork of the motor vehicle, conventionally on the roof of the motor vehicle toward the rear region, i.e. generally often just before the start of the rear window.
Modern generations of motor vehicle are distinguished by particularly large glass roofs, some of which are also referred to as panoramic roofs. They can comprise, in addition to a sliding roof, at least one unopenable glass roof lining, i.e. a corresponding glass roof, wherein a corresponding antenna can then be mounted on this electrically non-conductive glass roof.
For mounting an antenna of this type, a corresponding mounting region or portion is provided on the glass roof, conventionally in the form of a correspondingly large and electrically conductive counterweight surface which is pre-mounted on the panoramic or glass roof (or rear window) of the vehicle, in order to generate a corresponding antenna beam diagram.
An exemplary illustrative non-limiting implementation provides an improvement for antenna systems of this type, i.e. for external and/or roof antennas on vehicles, in particular on motor vehicles, with which improved beam shaping is possible.
An exemplary illustrative non-limiting implementation provides, using simple means, a significant improvement in the efficiency and the effectiveness of external and/or roof antennas on vehicles and in particular on motor vehicles.
An exemplary illustrative non-limiting implementation can in this case be used above all on electrically non-conductive outer linings of motor vehicles. Of particular importance are in this regard glass roofs, some of which are referred to as panoramic roofs on account of their large size. Likewise, the invention can also be used in other glass windows in a vehicle, in particular a motor vehicle, even in vehicle linings made for example of plastics material, and thus of electrically non-conductive materials, in contrast to bodywork metal sheets.
An exemplary illustrative non-limiting implementation proposes and provides an additional beam shaping means with which significant improvements with regard to beam shaping, and thus with regard to the receiving and transmitting properties of an antenna, can be achieved.
In an exemplary illustrative non-limiting implementation there is provided, generally on an electrically non-conductive portion of a bodywork lining, i.e. in particular on an electrically non-conductive motor vehicle roof or a motor vehicle window and the like, an antenna mounting region or portion, generally in the form of a sufficiently large electrically conductive counterweight surface.
In order to achieve the improved antenna properties, the manufacturer can itself now provide for the additional provision of an electrically conductive parasitic beam shaping means below the antenna mounting region or portion, i.e. above all also below a correspondingly electrically conductive counterweight surface in the material of the motor vehicle lighting or therebelow (i.e. in particular in the material of the glass roof or below the glass roof).
This parasitic beam shaping means is of a size and/or position such that it is not shielded by the antenna mounting region or portion or at least by the chassis of a corresponding motor vehicle antenna to be built on, i.e. that the region of the parasitic beam shaping means reaches, at least in certain portions, further than the chassis of an antenna means to be mounted or reaches further than the aforementioned electrically conductive counterweight surface which is generally several times larger than the base surface of a chassis of an antenna means to be mounted.
The electrically conductive parasitic beam shaping means are in this case not electrically connected to the chassis of the antenna means or the electrically conductive counterweight surface.
In an exemplary non-limiting arrangement, the design (i.e. the design looking from above on to the planar parasitic beam shaping means) can be unsymmetrical, based on the mounting region or mounting portion of the antenna (i.e. on the position of the motor vehicle to be mounted and/or the orientation thereof) and, precisely by an unsymmetrical configuration of the parasitic beam shaping means, an improvement with regard to the radiation diagram of an antenna can be achieved.
This can be advantageous especially when the antenna is provided for reception of circularly polarized electromagnetic waves, such as are used for example in the reception of GPS signals on the one hand or for example in the reception of what are known as SDARS signals on the other hand, i.e. before receiving satellite-supported information and/or radio systems. The SDARS system is for example a satellite-supported digital radio service system which is conventional in USA.
The exemplary parasitic beam shaping means can be of differing configuration. It can for example have a grid structure with “perforated grid properties”; in this way, a plurality of conductors running parallel to one another can for example be arranged in a singly or multiply rotated arrangement relative to one another; i.e. in this way, a first, a second and optionally a third, etc. parallel grid structures can be arranged so as to overlap and intersect one another, which grid structures are electrically connected to one another at their nodal points.
Also possible however is a grid structure consisting merely of electrically conductive linear portions running parallel to one another, i.e. thus forming not a “perforated grid” but rather a “strip grid”. Nevertheless, in all these cases, reference is sometimes made to a parasitic radiator surface or to a plurality of parasitic radiator surfaces, as this term best describes the parasitic beam shaping means.
Alternatively or additionally, it is also possible for the grid structure to consist of a large number of dot or circular areas (dots) or similarly configured “conductive islands” which are arranged sitting next to one another and thus produce a dot or island-type structure. The design of the individually conductive portions (dots) can be selected in different ways and does not necessarily have to be circular. Elliptical, symmetrical structures having round, convex and concave boundary lines and straight edge portions, etc., for example in the form of small squares and rectangles, hexagons, are also possible. To this extent, there are no limitations.
However, the aforementioned parasitic beam shaping means does not necessarily have to be implemented or embodied as a grid structure. Also possible is a parasitic radiator surface in the form of a self-enclosed area (in which for example individual, relatively large recesses could also be integrated), having elevated conductivity. This “closed area” can for example be a planar metal coating on the electrically non-conductive motor vehicle structure, preferably in the form of a glass window or panoramic window, a foil coated with metal or else a screen printed surface or the like which is electrically conductive. In addition, mixed systems with a grid structure and correspondingly larger closed areas having elevated electrical conductivity could also be provided.
Finally, it has also proven beneficial, but also sufficient, if the size of the parasitic beam shaping means is dimensioned in the manner of the aforementioned parasitic radiator surface or parasitic radiator surfaces in such a way that said parasitic beam shaping means has in the area surrounding the antenna a maximum extent which is for example not greater than 40 cm. However, in many cases, even smaller dimensions are sufficient, so that the parasitic radiator arrangement is provided in an area around the antenna that is not larger than 35 cm, 30 cm, 24 cm or 20 cm.
This parasitic radiator is preferably also produced by the manufacturer inside the plastics material, in particular inside a glass window intended for example for a glass roof or a rear window of a vehicle. This grid-like structure in the form of a parasitic radiator can however also be configured on the inside of the window and preferably also manufactured during the manufacturing process. Attachment to the outside is generally not desired simply because no electrical contact is intended to take place here with a counterweight surface which may be provided at this location and/or the electrically conductive chassis of an antenna to be built on.
As mentioned hereinbefore, a counterweight surface can first be provided, in particular on the glass receiving the antenna. The parasitic beam shaping means then extends around this electrically conductive counterweight surface and can in this case also be provided even below the counterweight surface. It is however also possible for the counterweight surface to be located for example within a cutout in the electrically non-conductive material of the vehicle structure, in particular in a cutout in a glass roof. The upper sides of the counterweight surface and of the glass roof can then lie at a common level, i.e. be flush with each other. In this case, the antenna connection cable would not penetrate the glass window, as the one or more electrical connection cables leading to the antenna can lead to the antenna directly via the counterweight surface and a cutout formed therein. The beam shaping means is located in this case below or laterally of the upper side of the counterweight surface. This provides a technically readily implementable and visually very attractive solution, wherein above all the upper side of the glass surface and of the counterweight surface can be flush or almost flush with each other.